Optical switch devices have been developed in which a movable shutter is mounted on a smooth flat substrate. The shutter is positioned such that light is directed toward the substrate in proximity to the shutter. The shutter is made of a thin material which has stresses introduced such that the shutter is normally in a coiled configuration. As a result, light directed onto the substrate is able to pass through the substrate without obstruction from the shutter. When a voltage is applied across the substrate and the shutter, the resulting electric field causes the shutter to uncoil into a flat position over the surface of the substrate. Light directed onto the substrate therefore impinges on the uncoiled shutter. Such a device can be implemented in a variety of optical switching applications.
For example, U.S. Pat. No. 5,233,459, issued on Aug. 3, 1993, entitled “Electric Display Device,” describes an optical switch device with a movable shutter. The shutter is formed on a glass substrate such that when the shutter is coiled up, light can pass freely through the device. When the shutter is uncoiled, it is held in a relatively flat state over the substrate by the electric field applied between the shutter and the substrate. In this state, light impinges on the shutter.
Such devices are prone to several drawbacks. For example, the shutter can have a tendency to stick to the substrate. When the electric field is removed or reduced, the sticking interferes with the ability of the shutter to recoil. This can cause substantial delays in devices and processes which utilize the device, or can result in complete failure of the devices and processes. Also, the gaseous atmosphere in which the device operates can slow the opening and closing of the shutter, also resulting in delayed processing. Also, the shutter can tend to distort when it is uncoiled.